!1217 sched/rt: Fix possible warn when push_rt_task

Merge Pull Request from: @ci-robot 
 
PR sync from: Hui Tang <tanghui20@huawei.com>
https://mailweb.openeuler.org/hyperkitty/list/kernel@openeuler.org/message/YBGT2EBOTBD7PFWTPX3DX74QNLLTRRVR/ 
 
 
Link:https://gitee.com/openeuler/kernel/pulls/1217 

Reviewed-by: Zucheng Zheng <zhengzucheng@huawei.com> 
Reviewed-by: Jialin Zhang <zhangjialin11@huawei.com> 
Signed-off-by: Jialin Zhang <zhangjialin11@huawei.com> 

kernel/sched/rt.c

@@ -1941,6 +1941,9 @@ static int push_rt_task(struct rq *rq)
 		goto retry;
 	}
 
+	if (unlikely(!cpu_online(lowest_rq->cpu)))
+		goto out;
+
 	deactivate_task(rq, next_task, 0);
 	set_task_cpu(next_task, lowest_rq->cpu);
 	activate_task(lowest_rq, next_task, 0);